The present invention is directed to a method and apparatus for assessing the motion of flat objects moved through a channel. In particular, the invention is related to such a method and apparatus where the measurement is based on the output of at least one anemometric sensor affected by the airflow associated with movement of the flat object.
Various conventional motion-checking methods are known in the art, e.g., methods of using electromechanical sensors (U.S. Pat. No. 6,220,103; U.S. Pat. No. 6,192,285; U.S. Pat. No. 5,814,778; U.S. Pat. No. 5,324,898, U.S. Pat. No. 4,687,928, etc.), ultrasound methods (U.S. Pat. No. 6,331,964; U.S. Pat. No. 4,414,591, etc.), methods of using piezoelectric sensors (U.S. Pat. No. 5400,012; U.S. Pat. No. 5,258,743 etc.,) capacitive and charge sensitive methods (U.S. Pat. No. 5,391,859, U.S. Pat. No. 4,833,281 etc.), methods of using microwave technique (U.S. Pat. No. 6,333,691, U.S. Pat. No. 4,981,158 etc.), methods of using pyroelectric sensors (U.S. Pat. No. 6,215,399; U.S. Pat. No. 6,163,025; U.S. Pat. No. 4,943,712 etc.), methods of using optical images (U.S. Pat. No. 6,219,455; U.S. Pat. No. 5,824,916; U.S. Pat. No. 5,212,379; U.S. Pat. No. 4,896,966; U.S. Pat. No. 4,099,886 etc.), and its computer processing (U.S. Pat. No. 6,317,136, U.S. Pat. No. 6,188,798; U.S. Pat. No. 5,568,203; U.S. Pat. No. 4,906,846 etc.), methods of using coherent lighting (U.S. Pat. No. 5,212,379; U.S. Pat. No. 4,334,777 etc.). It is difficult or expensive to use any of these methods for evaluating the movement of currency papers due to the changing,size, thickness, material, surface appearance, configuration and deterioration characteristics of currency paper. Currency paper, when moved through a channel, also has a significant vibration making the assessment more difficult.
U.S. Pat. No. 6,203,194 to Beerwerth et al., describes the thin film multipair thermopile sensor for multipurpose motion detector which is provided with diaphragms and/or focusing elements arranged so that a moving object focused images passes by the hot and cold junctions of the sensor element alternatively, causing a corresponding sensor output signal to be generated. However, this method needs a fixed lighting of testing objects and an extensive optical set for focusing a large object to the thermopile sensor.
It is known to include in paper transport arrangement, a paper jam detector (U.S. Pat. No. 4,734,744 and U.S. Pat. No. 4,203,589). An expensive array of optical sensors check the passageway for the absence of a paper sheet in the specified place at the specified point in time. However, all these detectors have a significant time delay between an actual paper jam and the detector identifying a paper jam.
Airflow detection using a previously heated anemometer is known (U.S. Pat. No. 6,101,872; U.S. Pat. No. 5,827,960; U.S. Pat. No. 5,710,380; U.S. Pat. No. 5,629,481; U.S. Pat. No. 5,558,099; U.S. Pat. No. 5,394,883; U.S. Pat. No. 5,272,915; U.S. Pat. No. 5,263,370; U.S. Pat. No. 5,094,105; U.S. Pat. No. 5,081,866; U.S. Pat. No. 4,884,215). However, the prior art detectors are complicated and designed for relative slow movement and cannot detect in real time, short weak airflow vibration typical of airflow vibration waves from leading and trailing edges of a banknote.
The present invention provides a contactless method of sensing the motion or unexpected stoppage of currency papers with arbitrary size, thickness and deterioration, by measurement of the airflow movement around moving currency paper or air movement associated with the unexpected stoppage thereof.
The present invention provides an apparatus for checking the currency paper motion including at least one sensor for real-time measurement of the speed changes of the airflow associated with the motion or unexpected stoppage of currency paper.
In a preferred aspect of the invention, the apparatus contains at least two airflow sensors for measuring the instantaneous speed changes of the airflow associated with the currency paper.
In a further aspect of the invention, the apparatus contains a line of airflow sensors and the signals thereof are processed to provide real-time position information of currency paper edges.
In an aspect of the invention, the apparatus contains a two-dimensional matrix of airflow sensors for detecting the real-time position of currency paper in a transporting channel.
According to yet a further aspect of the invention, a low cost failsafe compact planar heat-loss airflow sensor for sensing changes in airflow is provided.
A preferred motion checking apparatus, according to the present invention, is inexpensive and easily incorporated into banknote validators.
The real-time information about currency paper motion is used to control currency transportation and to reduce paper jams in validity checking machines, including validators, banknote dispensers, and automated payment systems for receiving and dispensing of banknotes.
The present invention provides an improved contactless method and apparatus for rapid and inexpensive motion checking of flat objects by detecting of air turbulence around the object especially adjacent its front and back edges. The objects need not be identical in surface appearance, configuration and deterioration. The objects preferably may be of substantially any size or thickness and need not be less than some maximum size or within some narrow range of thickness.
A contactless method of checking the motion or unexpected stoppage of flat objects according to the present invention includes measuring the instantaneous cooling rate of a previously heated thin sensor wire or small bead thermistor located in the airflow associated with the moving test object.
All objects that move through an atmosphere cause a corresponding tight-fitting air movement. Thin end moving flat objects produce front and back shock waves that are distinguishable from the almost uniform airflow associated with the middle portion of the object. Unexpected stoppage of a flat object causes vibrations of airflow, especially when objects are thin like currency papers. These shock and vibration airwaves produce a change in airflow which cools the heated thin metal wire with a corresponding decrease of its resistance xcex94R. The corresponding voltage drop on this wire xcex94U=Ixc3x97xcex94R where I is a current through wire. When NTC thermistor is used one can get the corresponding voltage increase. Alternating component of this signal is practically independent of any surrounding quasi-steady airflow and temperature, whereby the voltage drop is indicative of the motion status of the object.
In accordance with the present invention, an apparatus for motion checking of flat object includes at least one heat-loss sensor located parallel to one side of a testing object with the sensor connected to a steady current source and amplifier which forms a signal proportional to the instantaneous rate of sensor cooling.
Further in accordance with preferred embodiment of the present invention, the heat-loss sensor is connected to an alternating voltage amplifier through derivation circuit. The preferred time constants of amplifier and derivation circuit are similar to typical flat object motion time along the wire or to flat object oscillation period under unexpected stoppage.
Further in accordance with a preferred embodiment of the present invention, the said sensor includes a series of heat-loss elements connected sequentially and positioned at equal distances from one another and parallel to frontal edge of a testing object. To get the optimal time resolution of motion process optimal distance d between adjacent elements is less than d=3xcfx84xc3x97"ugr", where "ugr" is the rate of object movement, xcfx84xe2x80x94time constant of heated single sensing element.
Still further in accordance with a preferred embodiment of the present invention, the heat-loss sensor includes a two-dimensional xe2x8axa5-type matrix of heat-loss elements connected sequentially in each dimension parallel and perpendicular to frontal edge of the testing object respectively, each one-dimensional line of sensors is connected to its own steady current source and amplifier, to form a sequence of pulses in accordance with the testing object motion.
Further in accordance with a preferred embodiment of the present invention, the said sensor is a thin heat-loss sensing wire with a protective housing which accommodates a pulsed airflow under testing object unexpected stoppage.
Still further in accordance with preferred embodiment of the present invention, the apparatus has a semi-closed box with slot for flat object transportation and an air compensation opening with the heat-loss sensing wire associated with the air compensation opening.
Further in accordance with a preferred embodiment of the present invention, the planar heat-loss sensor is a thin mini PC-board with the heat-loss sensing wire alongside printed conductor on said PC-board verge, one sided ends of wire and printed conductor are connected together and another ends are connected to electric scheme such that currents in sensing wire and alongside conductor are equal and antiparallel.
Still further in accordance with a preferred embodiment of the present invention, the planar heat-loss sensor is a thin mini PC-board with two heat-loss sensing wires alongside to sharpened edge of mini PC-board, one sided ends of wires are connected together and another ends are connected to electric scheme such that currents in alongside wires are equal and antiparallel.
Further in accordance with preferred embodiment of the present invention, the needle-shaped heat-loss sensor is a thin hard metal stem with alongside heat-loss wire, one end of the stem is connected to wire and opposite stem and wire ends are connected to electric scheme through transition mini PC-board such that currents in alongside wire and stem are equal and antiparallel.
Still further in accordance with a preferred embodiment of the present invention, said sensor is a heat-loss small bead thermistor with thin protective coating.
Additionally in accordance with preferred embodiment of the present invention, there is provided a method for checking the time variation of flat testing object momentary speed, including the measuring of difference between instantaneous cooling rates of heat-loss sensor coursed by (located in) the airflow of the testing object airflow and reference heat-lose sensor, placed into undisturbed air.
Additionally provided, in accordance with preferred embodiment of the present invention, is apparatus for checking the time variation of flat testing object momentary speed, including at least two heat-loss sensors each being connected to a steady current source and to differential channels of amplifier, one sensor is situated in the testing object airflow and the other sensor located in undisturbed air for compensation of surrounding temperature and quasi-steady airflow. Steady current sensor""s feeding permit to stabilise its temperature, so the method sensitivity practically independent from object speeds.
Additionally in accordance with a preferred embodiment of the present invention, the apparatus includes at least one protective spacer between testing object and heat-loss sensing wire forming the cooling airflow according to movement rate of testing object.
Additionally in accordance with a preferred embodiment of the present invention, there is provided a method for locating the flat object including the formation of the directional to testing object airflow through matrix of air jets with heat-loss sensor in each and measuring instantaneous cooling rates of each sensor coursed by airflow through free jets and jets screened by flat object. The instantaneous cooling rates of sensors screened by testing object is less in comparison with sensors situated in free jets so it is easy to determine the real-time location of testing object and its motion behavior.
Additionally provided, in accordance with a preferred embodiment of the present invention, is apparatus for determine the real-time location of testing object including excess air pressure source, at least one-sided air jets matrix with heat-loss sensor in each jets connected to corresponding steady current source and amplifier, forming the signal proportional to instantaneous rate of sensor cooling.
Further in accordance with a preferred embodiment of the present invention, all heat-loss sensor are connected sequentially to steady current source at that sensor ends are connected through corresponding analog multiplexer to differential inputs of amplifier which forming the output signal respectively to instantaneous cooling rate of sensor situated in permitted channel address.
In operation, the currency paper is moved across the heat-loss sensor with its xe2x80x9cnarrowxe2x80x9d height dimension as the leading edge. The front and back shock waves cause rapid cooling of heated sensor so its resistance quickly changes and we get corresponding voltage drop on this wire xcex94U. The variable component of said signals amplified by alternating current amplifier. Point in signals time appearance corresponding to moment of paper front and back edges passing by the sensor wire. If the length L of currency paper is known its average speed may be easy determined as "ugr"=L/xcex94t, where xcex94t is the time delay between front and back signals. When the heat-loss sensor consists of plurality of sensing elements connected sequentially and situated on equal distances d1 from one another parallel to frontal edge of currency paper the average speed is "ugr"1=d2/xcex94t2, where xcex94t2 is the time interval between adjacent pulses. In two-dimensional xe2x8axa5-type matrix elements connected sequentially parallel to frontal edge of testing object operates by described above manner. Connected sequentially sensing elements in orthogonal dimension perpendicular to frontal edge of testing object and situated on the equal distances d2 indicates the transverse shift of testing object with corresponding speed "ugr"xe2x8axa5=d2/xcex94t2, where xcex94t2 is the time interval between adjacent pulses from orthogonal sensor. Protective housing round sensor wire prevents it against damage and channeling the airflow to the wire according to testing object motion. The instantaneous cooling rate of heat-loss sensor placed into tight fitting to testing object airflow allows determining the time variation of flat testing object momentary speed. Unexpected stoppage of thin testing object sourses causes deformation and vibration of the object and changes in the airflow associated with the object. The heat-loss sensor detects these changes and produces a corresponding pulse (multi pulse) signal. The planar anemometric sensor has good mechanical durability, technological effectiveness and low cost. The heating current in single or doubles wire planar and needle-shaped sensors flows in opposite directions in alongside thin wire and hard conductor causes the magnetic repulsive force. On the other hand under heating the sensor wire undergoes the thermal extension. Said wire moves away from another conductor (printed or hard) or sensor wire and mini PC-board. So the sensor sensitivity and response speed significantly rises. The formation at least one sided multiunit airflow to testing object with heat-loses sensors in each air jet allows location of the object and allows determination of the motion behaviour thereof.